The Big Sheep Mountain gold prospect is at the summit of Big Sheep Mountain, within the Shulaps Range, approximately 23 kilometres northeast of Gold Bridge B.C.
The prospect is hosted by feldspar and quartz-porphyritic rhyolite, which forms a 150-metre thick cap to a stock of feldspar porphyry and feldspar-hornblende porphyry. These rocks are thought to be Late Cretaceous to Early Tertiary. The stock intrudes sedimentary rocks of the Lizard Formation (part of the Lower Cretaceous Taylor Creek Group) and are bordered by minor greenstone of the Mississippian to Jurassic Bridge River Complex and minor serpentinite of the Permian and older Shulaps Ultramafic Complex.
The host rhyolite porphyry is argillic-altered (with a chalky appearance), fractured, and almost invariably limonite and manganese oxide stained. Pyrite is uncommon, and where present is generally very fine-grained and weathered. Locally, the rocks are tuffaceous to breccia-textured, vuggy and traversed by fine-grained quartz veinlets, stockworks and cavities, and rare amethyst veinlets. Altered rhyolite porphyry, with minor quartz veinlets and limonite coating, contains as much as 19.2 grams per tonne gold and 541.9 grams per tonne silver (Assessment Report 9952). These rocks contain no visible sulphide minerals. A rare vein of vuggy crystalline quartz with disseminated to massive tetrahedrite contains 9.5 grams per tonne gold and 11.3 grams per tonne silver (Assessment Report 10925). The nature of the hostrocks, alteration and mineral assemblages suggest a high level or epithermal environment of formation.
In 1980, Du Pont of Canada Exploration Ltd. staked the Big Sheep Mountain claims and collected 18 stream sediment samples, 38 soil samples and 15 rock samples. In 1981, Du Pont of Canada Exploration Ltd. conducted an exploration program consisting of geological mapping and collection and geochemical analysis of 249 soil samples and 21 rock samples. In 1982, Du Pont of Canada Exploration Ltd. completed geochemical soil and rock sampling. The claims were held in good standing until 1990 when they were forfeit. At that time the owner of the claims was CSA Minerals Inc. In 1992, Cogema Resources Inc. held the claims, but completed no work and dropped the property in 1993.
In 2002, Viceroy Resources Corp. staked the Big Sheep claims and completed geochemical soil and rock sampling. The soil sampling indicated anomalous gold values concentrated in northwest-trending structures near the summit of Big Sheep Mountain. Viceroy Resources Corp. allowed to claims to lapse.
In 2004, Tom Gilchrist staked the Big Sheep property. In 2007, he completed access trail improvements and geochemical soil, rock and stream sediment sampling. In 2008, he conducted geochemical soil, rock, stream sediment and moss mat samples. Highlights of the rock sampling include sample 126869, which assayed 7.27 grams per tonne gold, greater than 100 grams per tonne silver, greater than 1 per cent lead and 0.44 per cent zinc (Assessment Report 30486). In 2010, he completed rock and soil sampling and compiled geological observations. In 2012, he conducted an exploration program consisting of the collection of 21 rock samples. A float sample of gossanous rhyolite with limonite and goethite alteration assayed 30.2 grams per tonne silver and 0.46 per cent lead (Assessment Report 33619). Soil and rock geochemical and prospecting programs continued below north and east aspects of Big Sheep Mountain in 2014 and 2019.
